Why Does Garlic Make Your Breath Smell So Bad?

Garlic is tasty, but its flavor comes at the cost of alienating your dinner partners with a distinct odor on your breath—and even your skin—when the meal is done. How do these innocent-looking little bulbs cause so much trouble?

Garlic breath isn’t so much garlic’s fault as our own. The chemicals responsible for the stink aren’t present in whole garlic cloves, but are only formed when the clove is damaged. Chopping or crushing garlic releases an enzyme called allinase, which converts odorless alliin molecules into pungent, sulfurous allicin.

Allicin is the major contributor to the aroma of fresh-chopped garlic and also gets the ball rolling on garlic breath. It’s unstable and quickly breaks down into several other smelly sulfur-containing compounds—including diallyl disulfide, allyl methyl sulfide, allyl methyl disulfide, and allyl mercaptan—that hang out in the air in your mouth and make your breath stink.

Your body metabolizes most of these compounds within a few hours, but allyl methyl sulfide is slower to break down and stays in the body longer than the others—sometimes up to a day or two. From the gut, it slips into the bloodstream and moves freely about your body. It gets circulated to the lungs and shows up on your breath again, and also makes its way into your sweat and urine, giving them a garlicky odor.

Garlicky sweat can cause some other issues aside from the smell. Doctors in the UK reported the case of a patient who made china dolls and complained of black speckles showing up on the dolls’ heads after she handled them. The doctors found that the patient ate a lot of garlic and that her body wasn’t very good at metabolizing the various sulfur compounds, allowing them to be “excreted virtually unchanged in her sweat.” When she touched the dolls with sweaty hands, the garlic compounds reacted with flecks of iron in the clay the dolls were made from, resulting in black splotches.

Now that you know what causes garlic breath, what can you do about it? Brushing your teeth after you eat garlic can rid your mouth of some of the smelly compounds, and you can also mask them with a stronger, more pleasant smell until they break down. There’s also some research that suggests that eating certain other foods—kiwi fruit, spinach, lettuce, parsley, basil, mushrooms, milk and rice—can help reduce garlic breath by degrading, trapping and/or deodorizing the sulfur compounds.